Hawaii’s largest city long has been a top vacation destination for its climate and beauty. But the city also works well as a plush retirement venue. Some 18% of its 390,000 residents are of retirement age. Its seemingly modest financial demographics—average home price of $500,000 and median household income of $60,000—masks some considerate extremes at the high end in such neighborhoods as Waialae, Kahala, Nu’uanu and Pauoa, full of homes going for $1 million and up.